Various types of sealing devices exist for sealing opposing surfaces. Known seals include metallic sealing devices, which are commonly made of materials such as soft iron, carbon steel, stainless steel, high nickel alloy, Inconel or Nimonic alloys. To improve their sealing ability, the sealing surfaces of these known metallic seals can be coated with a deformable material, such as polytetrafluoroethylene (PTFE), gold, silver, copper, and the like.
Known metallic seals can be variously shaped, such as a metallic O-ring, and can have cross-sections of various shapes. For example, a “C” seal or spring-energized “C” seal is typically an annular seal having a “C”-shaped cross section. Known “E” seals are generally annular in configuration and have an “E” shaped cross-section. Other types of seals having cross sections which are parabolic, convoluted, Y-shaped, or omega-shaped (Ω-shaped) are also known. Some of these seals are designed to be more resilient than others, e.g., different seals are designed to achieve different sealing characteristics.
Although metallic seals of the type described generally function suitably in certain applications, these types of metallic seals have drawbacks. A coating is sometimes applied to these seals to enhance sealing characteristics, especially for use at high temperatures and pressures. For example, some metallic seals are often coated with a deformable material (e.g., PTFE, gold, silver, copper, and the like) in order to achieve the desired sealing integrity. Typically, seals for use in these applications are coated per AMS 2411 in which silver is deposited on a metallic seal with a gold strike between the base metal and the silver deposit to withstand temperatures of up to 1400° F. (760° C.). According to the AMS specification, small blisters of less than 0.015″ on the deposit are acceptable.